1. Field of the Invention
The present invention relates to a force control for controlling a load-handling device that includes an hydraulic gripper adapted on the one hand to firmly grip objects, such as one or more rolls or bales of paper material or other goods, through the medium of pressure in a clamp pressure line leading to one or more hydraulic cylinders that actuate gripper-mounted gripping arms, and on the other hand to lift said objects by actuation from a lifting device.
2. Description of Background Art
Great demands are placed on paper-rolls, particularly for printing presses, that the rolls will not be squeezed to an oval shape during handling of the rolls from a paper mill to a printing department. For instance, the tolerance placed on a roll 125 cm in diameter may sometimes be as narrow as 2 mm measured on the radius of the roll. Different solutions have been proposed in endeavours to optimally control the clamping force of the gripper against the roll periphery. EP-A-0664272 and FI-B-84715, among others, teach devices for controlling the clamping or gripping forces in response to detected sliding at the gripping surfaces.